Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.93	11.825%	$190.0242	$190.02	$190.00	$190.00
Purchase #2	$159.94	7.811%	$172.4329	$172.43	$172.45	$172.40
Purchase #3	$132.63	8.508%	$143.9142	$143.91	$143.90	$143.90
Purchase #4	$139.55	10.569%	$154.299	$154.30	$154.30	$154.30
Purchase #5	$234.29	13.285%	$265.4154	$265.42	$265.40	$265.40
Purchase #6	$185.93	7.203%	$199.3225	$199.32	$199.30	$199.30
Purchase #7	$65.40	8.281%	$70.8158	$70.82	$70.80	$70.80
7 purchase totals =	$1,087.67		$1,196.2240	$1,196.22	$1,196.15	$1,196.10